rather unexpected tube findings

[phsyconoodler]

I was doing a listening test with every preamp tube I have,about 30 in all,in my Vibrolux reissue amp and the results I got were interesting to say the least.
  I have everything from Amperex bugle boys to Mullards,Sylvania,Phillips,GE etc....
I tried them all in V2,the reverb channel,of my amp with my strat equipped with lace sensor pickups.Emerald,silver and purple in the bridge.
  The amp has two 10" eminence Alnico speakers that Fender uses in production amps.Not my favorite but not bad at all.
Nearly every tube was brighter than the stock Sovtek,with more chime but I had to turn the treble almost off to get it to stop ripping my ears off.Treble BITE is the word here.Even the Mullards were bright.
  After much listening and swapping,playing the same licks over and over,the best sounding tube to my ears was a (drum roll please)
a SOVTEK 12AX7 LPS.
  Hands down it had the best lows,best mids and by far the best highs for chording and single notes.
I was very surprised that some of my NOS treasures were not nearly as nice in this amp.
  I had the same settings for every tube so it's not a case of psyco-acoustics.
The differences were not subtle at all.They were dramatic in the extreme.
  But the best TONE of all came from a Mullard ECC82 tube.However the gain was not sufficient and it rendered the normal channel inoperative.The shared cathode is likely the issue there.
  The amp is a Custom Vibrolux and has reverb and trem in both channels.I play primarily in the bright channel.I did not try any tubes in the normal channel.

  

[simonallaway]

Breaking news: In after-market trading, Sovtek stock price quadruples at news of "The Phsyconoodler Report".

[phsyconoodler]

More likely it will be on the next 'Mad TV' episode.

[John]

Dang, and JUST shorted that stock!

[bigdaddy]

That's why I stopped using NOS tubes. The prices were way out there and you never knew what you really got. I had so many quit on me, some at gigs. Yes they sounded better but not that much better and not all did over new tubes.

It really all depends on the guitar you play and if you use pedals, what music you play, what sound you want, what pickups are in the guitar, how you set the amp, what amp, what speakers, what size strings on the guitar and more.

I'm not at all surprised at your findings. I am familiar with those amps and unless you dime the volume it's a very treble spiked amp with those speakers, even worse with a pair of RI Jensen C10Qs. I owned one along with the RI Vibroverb and RI BFDR, with the right speakers, tubes and bias those amps all sounded pretty good. Once you're playing at a gig with a whole band so much of those little nuances that you hear disappear at volume when you're fighting the drummer for stage volume or a notey bass player. In fact you might end up turning that treble knob up when the bass player decides to use that horn in his 4x10 cab.

That's reality......

[HotBluePlates]

I'd suggest measuring the gain of each of the tubes and comparing the result to what you get with the Sovtek 12AX7LPS. This can be done with a signal input of some kind (sine is standard but not mandatory) and doing a a.c. voltage measurement on the grid and at the plate. Also, measure the idle current and bias by a simple voltage measurement across the cathode resistor.

I have wondered a long time about exactly what contributes to the sonic differences between tubes. I have a large assortment of old-production tubes (some NOS, some just used older types) that I've acquired over years for less money than what NOS dealers charge. Regardless of the fact that a certain selection of these tubes has a sound that most new tubes can't match, I'm all for finding the way to select good new tubes that provide great sound without paying the prices that some dealers charge for NOS stuff.

I plan on eventually doing this kind of testing myself. I have a good Gm tester, but I also have the gear to characterize tubes more fully and plan to see if there's a correlation between good sonics in-circuit and an out-of-circuit test.

The main suspicion I have is that the gain or Gm is different among tubes that show sonic differences in an amp.

Of course, not all of the old tubes sound great in every circuit.

[pullshocks]

Thanks for posting your evaluation.  The Sovtec might be just the thing for a couple of amps that are brighter than I like.

[mackie2]

HBP--

I have done a lot of experimenting with tubes since the 1950's--Audio and  Transmitting tubes.
Amp design has engineering  economics at the top of its list.

One of the best sounding preamp tubes, I have experimented with was the Western Electric 417 triode (Raytheon 5842)
We used this tube in Radar equipment in an IF receiver.  It has a mu of maybe 40, and it is a single triode.  I have an amp with  that tube, as the input tube, it has a velvet  chocolate tone. By the way, the new Western  Electric web site still
has this tube in manufactured list--over $300.

I found this tube  operated well with a 10k input resistor (Close to guitar Z) and 5K  plate resistor with 120v B+.  The NOS 5842's prices have gone through the roof, with the audiophile people doing their thing. 

I have always believed, most guitar amp designs, lost the concept of tone,  when they design the first stage with 100 mu tube-- then loose  most of that gain to passive tone circuit. Some old school tone designs used active stacks yielding gain
instead of loss.  Also used inductors for low and low mid frequency separation, etc.

Active tone control could mean, we don't have to have so much  gain--S/N  ratio's will improve--MILLER EFFECT along with  inter-electrode capacitance, compounds frequency response problems.

Anyway, enough of my rambling from the  old school,

Mackie2

[birt]

if you have some nice active tone circuits for guitar amps, please share them

[bigdaddy]

I like the sound of the 6AT6/6AV6 driving a 5879 or 6SJ7 in SE amps.

[PRR]

> lost the concept of tone,  when they design the first stage with 100 mu tube-- then loose  most of that gain to passive tone circuit

Not sure that hurts "tone".

But not sure that 12AX7 is the best ever made.

Who is good with little bits of metal? The 7077 looks like a dandy preamp, but you are gonna hafta invent a "socket" out of bits of brass and ceramic.

http://www.mif.pg.gda.pl/homepages/frank/sheets/149/7/7077.pdf

It is also notorious for very low noise (hiss) at UHF and also in the flicker range.

At 1mA it has 3 times the transconductance of 12AX7, albeit at Mu nearer 60.

It could instead be worked near 3mA, Gm=10,000uMho, Rp=16K, Mu=75. This would allow a lower-impedance tone-stack.

However: $65.

And no glow.

[zendragon63]

"...The 7077 is especially suited for use where unfavorable conditions of mechanical shock, mechanical vibration and nuclear radiation are encountered."

I might be able to live without the glow if it can survive 20 megatons of nuclear fission... 

Regards

dennis

[mackie2]

All--

I have some of those old triodes(don't remember the number--Sluckey may) used as RF amplifiers in ATCBI-3 in the attic--I was going to make a mic with the tube in--never got around to it.

Some old 50's Hi-Fi BOOKS had a lot of active tone ckts--They may not be better, but allow one to keep the gain rather than attenuate, as do the passive ckts. Every component the signal passes through, adds an imprint of either voltage or frequency change -- or both.

Below is an experimental amp using the 5842--Actually, a tele of mine, sounded pretty good through it--I never refined the ckt--Note the 6SN7 outputs--Volume is split Hi-Lo with a choke in one--I later built  the same amp with BI-Amp after the first stage.

Mackie